Conventionally known is a composite molded article comprising a metal member using metal as a base material and having a surface, and a resin portion coated on the surface of the metal member (PTL 1 to PTL 3). According to PTL 1, a composite molded article is formed by applying chemical etching to a surface of a metal member and then forming a resin portion by inserting the metal member and injection molding a thermoplastic resin in order to coat the etched surface with the resin. This literature states that even if a thermal cycle is repeated, the composite molded article can secure high airtightness. PTL 2 discloses a composite molded article formed by applying chemical conversion treatment to a surface of a metal member formed of a magnesium alloy to form a surface layer comprising metal oxide, metal carbonate, or metal phosphate, and then coating concavities and convexities of the surface layer with a resin layer containing polybutylene terephthalate resin or polyphenylene sulfide resin as a main component. In this article, a number of cylinders having a diameter of about 10 nm and a length of about 100 nm are formed on the surface layer. PTL 3 discloses a joining method in which, while a metal member formed of a metal material and a resin material are overlapped, the resin material located at a joint portion is heated to 200 to 1500 deg. C. by using a laser beam, thereby generating air bubbles in the resin material at the joint portion. The air bubbles have sizes of 0.01 to 5.0 mm. This literature states that this joining method can increase joining strength of the metal member and the resin material.    [PTL 1] Japanese Unexamined Patent Publication No. 2001-225352    [PTL 2] Japanese Unexamined Patent Publication No. 2007-301972    [PTL 3] International Publication No. WO 2007/029440